1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of manufacturing the liquid crystal display device.
2. Description of the Related Art
The liquid crystal display device has been used as a display element for various purposes because the liquid crystal display device has advantages of small thickness, light weight, and low power consumption. Recently, the uses of the liquid crystal display device have ranged widely from large television sets for household use to small portable terminals, and increasingly severe characteristics have been demanded of display elements.
There has been a growing demand especially for a wider viewing angle.
Accordingly, in place of a TN mode in related art, an IPS (In-Plane Switching) mode of a horizontal electric field system (see Japanese Patent Laid-Open No. Sho 63-21907, for example), a VA (Vertical Alignment) mode (MVA) in which multi-domain alignment is performed (see Japanese Patent Laid-Open No. Hei 10-186330, for example), and the like have been proposed.
Of these modes, the VA mode typified by MVA is a mode of high productivity because liquid crystal molecules are aligned perpendicularly to a substrate, and thus a high CR is easily obtained and a cell gap control margin is wide, for example. A method is disclosed in which a dielectric structure is provided as means for divided alignment in a pixel part, or a notch or a slit is provided in a transparent electrode (for example ITO: Indium Tin Oxide) part of a pixel, whereby the alignment of liquid crystal molecules is controlled using a resulting oblique electric field (see Japanese Patent Laid-Open No. 2005-266778, for example).
Accordingly, as shown in a plan layout schematic view of FIG. 10A and a sectional view of principal parts of FIG. 10B, notches are made in pixel electrodes 12 and 32 within one pixel 40, whereby the pixel 40 is divided into a plurality of sub-pixels. An alignment control factor (for example a dielectric structure) 34 or the like for alignment control is disposed in such a manner as to be situated at the center of each of the divided sub-pixels 50 (51, 52, and 53) on a pixel electrode (common electrode) 32 on a counter side. Thereby liquid crystal molecules can be aligned radially with the alignment control factors 34 provided on the pixel electrode 32 as a center within the sub-pixels 50. Because the liquid crystal molecules 22 are aligned radially, change in luminance as viewed from the direction of an azimuth angle is reduced, and thus a wide viewing angle performance is obtained.
However, when one pixel is divided into a plurality of sub-pixels, the sub-pixels need to be electrically connected to each other. The above-mentioned document discloses a method of leaving a pixel electrode (common electrode) at the central part of the sub-pixels. According to this method, while the direction of alignment is controlled by the alignment control factors provided on the counter electrode within the sub-pixels, the electric connecting parts are in a state of weak alignment control. When the liquid crystal panel is pressed, for example, the alignment is disordered as shown in a photograph of FIG. 11B. The alignment of liquid crystal molecules at a connecting part falls in a direction different from that before the surface pressing, and therefore the alignment of the sub-pixel is disordered, resulting in an alignment defect. Incidentally, a photograph of FIG. 11A shows that alignment disorder does not occur in a state in which the surface of the liquid crystal panel is not pressed.
That is, as shown in FIGS. 10A and 10B, a pixel in related art needs to have a pixel electrode (connecting part) for an electric connection between sub-pixels. However, because of absence of a factor defining the alignment of the connecting part, the state of the alignment becomes unstable. When the alignment is forcedly disordered by surface pressing or the like, the alignment does not return from the state of the alignment disorder.
FIG. 12 is a schematic diagram of an example of alignment disorder. Thus, liquid crystal molecules 22 do not return from a state of alignment disorder. Therefore a phenomenon representing a display abnormality in which a mark is left in the panel is observed. This phenomenon of the display abnormality can be alleviated by increasing a distance between sub-pixels 50. However, when the distance between the sub-pixels 50 is increased, a problem of a decrease in transmittance occurs.